The present invention relates to a drilling assembly, and more particularly to the central region of a drilling head assembly for boring into formations.
U.S. Pat. No. 5,366,031 to Richards, which is herein incorporated by reference for all that it contains, discloses an auger with a boring head having an arrangement for cutting relatively hard earth formations such as rock. First and second groups of drill bits are mounted to the boring head such that when the head is rotated, each bit in those groups cuts a different path at a different height to provide more than 100% coverage of the work surface being cut, while stabilizing the auger by distributing the down force of the auger over the entire bit rotation. The drill bits also are oriented to ensure bit rotation at relatively large attack angles (the angle the bit forms with the work surface there beneath) of about 50° to 60° to enhance auger penetration rates without detracting from the bit sharpening effect that results from proper bit rotation.
U.S. Pat. No. 3,821,993 to Kniff, which is herein incorporated by reference for all that it contains, discloses an auger arrangement for boring holes in earth formations in which the auger comprises a body with a central cutter arrangement including a pilot cutter on the axis and with laterally extending wing portions on the auger, on each of which is pivotally mounted a wing cutter arranged to swing outwardly when the auger rotates in cutting direction and to swing inwardly when the auger is not rotating or when it is rotating in the reverse direction so that the auger can readily be withdrawn from a hole bored thereby.
U.S. Pat. No. 3,763,942 to Levitt, which is herein incorporated by reference for all that it contains, discloses an auger or boring head, especially for horizontal rock and earth drilling having a circular ring of circumferentially spaced tool bits or teeth, a plurality of spokes or fins with leading ends carrying tool bits or cutting teeth in convex curved or arcuate contours from a central cutting point forwardly of the ring to the periphery of the ring. The cutting teeth on the ring project radially outward from the periphery thereof and are tilted forwardly in the direction of rotation of the auger head. The cutting teeth on the spokes or fins project forwardly, are tilted toward the direction of rotation of the heard and are also tilted backwardly to present the tip end of each tooth in a straight forward direction to the surface while it is cutting. In addition, the teeth are staggered so that successive teeth will not have the same cutting track. A head or socket is provided in the center of the auger head for connection to a drill rod or stem. Large open areas are provided through the ring between the spokes or fins, and the earth or rock cut by the head is free to flow through these spaces to a spiral conveyor which preferably has it leading edge behind one of the spokes or fins.
Examples of auger assembly from the prior art are disclosed in U.S. Pat. No. 2,981,403 to Goodrich, U.S. Pat. No. 2,800,302 to McCleannan, U.S. Pat. No. 4,917,196 to Stiffler, U.S. Pat. No. 5,794,727 to Murray, which are all herein incorporated by reference for all that they contain.